Why is this bad topology happening
There are a lot of faces overlapping, or vertices that seem to be part of a face but actually are not, etc, you didn't model it the right way. Also, as pointed out by Lemon, you use a Mirror modifier but your mesh go beyond the center of the mirroring. Maybe re-do it from scratch, and maybe follow some basic tutorials about modeling.
If I just take one example: If I select this vertex...

... and then move it...

... we can see that it was not part of the face.